We present here a selection of abstracts related to the subject of a review by J.M. Thresh, G. W. Otim-Nape, M. Thankappan and V. Muniyappa on 'The mosaic diseases of cassava in Africa and India caused by whitefly-borne geminiviruses' from the Review of Plant Pathology. The review considers the aetiology, transmission, incidence, effects, epidemiology and control of the cassava mosaic diseases.
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- Viruses of Plants A Brunt, Horticulture Research International, Littlehampton, UK, K Crabtree, M Dallwitz, CSIRO, A Gibbs and L Watson, Australian National University
TI: Cassava and genetic engineering: new genes for an old crop.
FT: Manioc et génie génétique: De nouveaux gènes pour une culture vivrière millénaire.
AU: Fauquet, C.\ Taylor, N. J.\ Schöpke, C.\ Cunnac, S.\ Masona, M. V.
JN: ORSTOM Actualités
YR: 1998
NO: No. 55
PP: 15-22
LA: Fr
AA: Orstom, International Laboratory for Tropical Agricultural Biotechnology (ILTAB), Scripps Research Institute, San Diego, California.
AB: An account of research undertaken by ILTAB into the application of genetic engineering techniques to cassava (Manihot esculenta) breeding is presented. Overall aims are food security for subsistence farmers and possible new prospects for marketing the crop. Particle bombardment and Agrobacterium transformation techniques have been used to produce lines containing a gene for resistance to CsCMV [cassava common mosaic potexvirus], a serious disease in Brazil. Plants containing putative ACMV [Cassava African mosaic bigeminivirus] resistance genes are undergoing analysis and a wild rice gene that confers resistance to rice bacterial leaf blight [Xanthomonas oryzae] is also being transferred to cassava.
DE: disease resistance\breeding programmes\genetic engineering\genetic transformation\cassava common mosaic potexvirus\Cassava African mosaic bigeminivirus\Agrobacterium\biolistics\Manihot esculenta\cassava\Xanthomonas oryzae\plant viruses\plant pathogenic bacteria\plant diseases\plant pathogens
AN: 0P06807019\7B01003571
TI: Whiteflies on cassava and its role as vector of cassava mosaic disease in India.
AU: Palaniswami, M. S.\ Nair, R. R.\ Pillai, K. S.\ Thankappan, M.
JN: Journal of Root Crops
YR: 1996
VL: 22
NO: 1
PP: 1-8
LA: En
MS: 29 ref.
AA: Central Tuber Crops Research Institute, Trivandrum 695 017, India.
AB: Biology and ecology of Bemisia tabaci, a vector of cassava mosaic virus [African cassava mosaic geminivirus] (CMD) in India, is briefly reviewed. Aleurodicus dispersus is also described.
DE: Bemisia tabaci\insect pests\cassava\Manihot esculenta\vectors\plant diseases\transmission\life history\Aleurodicus dispersus\plant pests\plant viruses\African cassava mosaic geminivirus
GL: India
TI: The incidence and severity of cassava mosaic virus disease in Uganda: 1990-92.
AU: Otim-Nape, G. W.\ Thresh, J. M.\ Shaw, M. W.
JN: Tropical Science
YR: 1998
VL: 38
NO: 1
PP: 25-37
LA: En
MS: 29 ref.
AA: Namulonge Agricultural and Animal Production Research Institute, PO Box 7084, Kampala, Uganda.
AB: A survey of the incidence and severity of cassava mosaic virus disease (CMD) [cassava African mosaic bigeminivirus, ACMV] was carried out in 30 districts of Uganda during 1990-92. Three counties of the 4 or 5 in each district were selected at random and 15 fields were sampled in each county. Records were taken of variety, CMD incidence and severity, and numbers of adult whitefly (Bemisia tabaci) on representative shoots. CMD occurred in all the 1350 fields examined, except 5 in Mpigi district. Disease incidence and severity varied significantly (P=0.01) between districts and between counties within districts. The overall incidence was <20% in 4 districts and exceeded 85% in 5. The incidence in fields in Masindi district planted 5 months earlier with CMD-free cuttings of the variety Ebwanateraka was as high as in unselected local material of the traditional varieties that had been grown in the area for many years. This suggested rapid spread of CMD and that Ebwanateraka was more susceptible than the traditional varieties. There were significant differences between adult whitefly population densities in the districts; numbers were greatest in Apac district where CMD was prevalent, and in Mbarara district where the incidence was much less. Significant differences in whitefly population densities were detected between counties sampled at the same time within some of the districts. The high incidence and severity of CMD in most districts confirm the importance of the disease in Uganda. Its impact on yield and productivity, recent changes in incidence and possible control measures appropriate for the different regions are discussed.
DE: plant diseases\plant pathogens\plant viruses\Manihot esculenta\cassava\viruses\Aleyrodidae\cassava African mosaic bigeminivirus\Bemisia tabaci\disease resistance\varietal reactions\Bigeminivirus\transmission\insect vectors\disease transmission
GL: Uganda
TI: Recombination between viral DNA and the transgenic coat protein gene of African cassava mosaic geminivirus.
AU: Frischmuth, T.\ Stanley, J.
JN: Journal of General Virology
YR: 1998
VL: 79
NO: 5
PP: 1265-1271
LA: En
MS: 24 ref.
AA: Universität Stuttgart, Biologisches Institut, Lehrstuhl für Molekularbiologie und Virologie der Pflanzen, Pfaffenwaldring 57, 70550 Stuttgart, Germany.
AB: Nicotiana benthamiana was transformed with 3 different constructs (pCRA1 pCRA2 and pJC1) containing the coat protein coding sequence of African cassava mosaic virus (ACMV) [cassava African mosaic bigeminivirus]. Transformed plants were inoculated with a coat protein deletion mutant of ACMV that induces mild systemic symptoms in control plants. Several inoculated plants of transgenic lines CRA1/3, CRA1/4, CRA2/1 and CRA2/2 developed severe systemic symptoms typical of ACMV. DNA analysis revealed that, in these plants, recombination had occurred between the mutant viral DNA and the integrated construct DNA, resulting in the production of recombinant virus progeny with 'wild-type' characteristics. No reversion of mutant to 'wild-type' virus was observed in pJC1-transformed plants. Recombinant virus from several transgenic plants was analysed by PCR and parts of DNA A of virus progeny were cloned. Sequence analysis revealed that only a few nucleotides were changed from the published sequence.
DE: plant diseases\plant pathogens\plant viruses\cassava African mosaic bigeminivirus\Nicotiana benthamiana\molecular genetics\genetic transformation\induced resistance\recombination\DNA\coat proteins\polymerase chain reaction\nucleotide sequences\symptoms\mutants
TI: Efficient whitefly transmission of African cassava mosaic geminivirus requires sequences from both genomic components.
AU: Liu SiJun\ Bedford, I. D.\ Briddon, R. W.\ Markham, P. G.
JN: Journal of General Virology
YR: 1997
VL: 78
NO: 7
PP: 1791-1794
LA: En
MS: 24 ref.
AA: Department of Virus Research, John Innes Centre, Colney Lane, Norwich NR4 7UH, UK.
AB: Clones of the common strain of tomato golden mosaic bigeminivirus (csTGMV) and cassava African mosaic bigeminivirus, originating from Kenya (ACMV-K), were non-transmissible by whiteflies. Lack of transmissibility of cloned ACMV-K was investigated by exchanging genomic components with a whitefly-transmissible ACMV isolate from Nigeria (ACMV-NOg). Neither pseudorecombinant was transmissible, suggesting that defects in both genomic components contributed to the lack of transmissibility. Analysis of the acquisition of the pseudorecombinants by Bemisia tabaci suggested that accumulation of virus within the insect was DNA B dependent. The return of the virus to plants was determined by DNA A, although the coat protein was essential for acquisition. Repeated passaging of both the wild strain of ACMV-NOg and the cloned virus led to loss of insect transmissibility of the wild isolate but not the cloned virus. It is concluded that products encoded on both genomic components are required for transmission of bigeminiviruses by B. tabaci.
DE: cassava African mosaic bigeminivirus\transmission\tomato golden mosaic bigeminivirus\Bemisia tabaci\insect pests\disease transmission\disease vectors\plant diseases\plant pathogens\plant viruses\Nicotiana benthamiana\Nicotiana tabacum\tobacco\coat proteins\DNA\cloning
AN: 0E08604321\0M07703724
TI: Pathogenesis-related proteins in cassava mosaic disease.
CT: Tropical tuber crops: problems, prospects and future strategies [edited by Kurup, G. T.; Palaniswami, M. S.; Potty, V. P.; Padmaja, G.; Kabeerathumma, S.; Pillai, S. V.].
AU: Bala Nambisan
YR: 1996
PP: 375-379
BN: ISBN 1-886106-37-1
LA: En
MS: 16 ref.
AA: Central Tuber Crops Research Institute, Trivandrum, India.
AB: The role of virus-induced proteins in the pathogenesis of cassava mosaic disease [cassava Indian mosaic bigeminivirus] was examined. The soluble and total protein profiles of healthy and diseased cassava leaves were studied to identify new proteins asociated with virus infection. Soluble proteins were extracted using acid (pH 2.8) and alkaline (pH 8.0) buffers, and total protein with buffer containing SDS and 2 MCE. Higher amounts of protein could be solubilised from diseased leaves than from healthy leaves. On analysis of the acid-soluble proteins using SDS-PAGE, 4 new protein bands corresponding to average molecular weights 20, 24, 29 and 35 kDa were observed in diseased leaves of cultivar H 226. An increase was also observed in the total soluble protein fraction from diseased leaves. Electrophoretic studies revealed 5 new protein bands with average molecular weights corresponding to 18, 22, 24, 29 and 50 kDa in cultivar H 226. The molecular weight of some of these new proteins is similar to some low molecular weight proteins produced in response to stress. Whether these proteins are host specific, formed in response to virus infection, or are associated with the virus, has yet to be established.
DE: plant diseases\plant pathogens\plant viruses\cassava Indian mosaic bigeminivirus\cassava\pathogenesis-related proteins
TI: Degeneration of cassava planting materials due to CMD.
CT: Tropical tuber crops: problems, prospects and future strategies [edited by Kurup, G. T.; Palaniswami, M. S.; Potty, V. P.; Padmaja, G.; Kabeerathumma, S.; Pillai, S. V. (Editors)].
AU: Thankappan, M.\ Nair, N. G.\ Nair, R. R.
YR: 1996
PP: 370-374
BN: ISBN 1-886106-37-1
LA: En
MS: 14 ref.
AA: Central Tuber Crops Research Institute, Trivandrum, India.
AB: Information on the rate of degeneration of cassava planting materials due to cassava mosaic disease (CMD) and successive loss in tuber yield was gathered from field trials for 3 seasons (1989-1992) using 3 cassava cultivars, Malayan-4, H 165 and H 226. Both primary and secondary spreads of CMD progressively increased in all the varieties during the successive crops. The reduction in growth and tuber yield due to CMD progressively increased and was proportionate to the increase in disease spread and incidence. The rate of spread and degeneration of cassava varied among the varieties. H 226 was the most vulnerable to degeneration followed by H 165 and M4. The study suggests that selection of disease-free planting materials and roguing of infected plants should be undertaken every year to contain CMD to a reasonable level.
DE: plant diseases\plant pathogens\plant viruses\cassava\epidemiology
TI: Effect of secondary infection of cassava mosaic disease on growth and tuber yield of cassava.
AU: Jeeva, M. L.
JN: Journal of Mycology and Plant Pathology
YR: 1997
VL: 27
NO: 1
PP: 78-80
LA: En
MS: 6 ref.
AA: Central Tuber Crops Research Institute, Trivandrum 895 017, Kerala, India.
AB: A quantitative assessment of various growth characters was made on healthy and diseased plants of 5 cassava varieties (H-97, H-165, Sree Visakham, Sree Sahya and M4). These varieties were raised from disease-free planting materials. The plants were free of cassava mosaic disease (CMD), caused by cassava Indian mosaic bigeminivirus, for the first 2 months and they contracted CMD through secondary infection from the third month onwards. At 6 months, plant height, stem girth, total number of leaves, number of lobes per leaf, petiole length and width were measured on 10 randomly selected healthy and diseased plants of each variety. Yield data were collected after 9 months. All the growth characters studied and the tuber yields were significantly (P=0.05) affected by CMD when all the varieties were considered together. The effect of CMD, however, varied with the variety. It is concluded that secondary infection of CMD during the growth period, besides serving as a source of inoculum, reduces growth and yield of cassava although the disease caused by the secondary infection is not as severe as that caused by primary infection.
DE: plant diseases\plant pathogens\plant viruses\cassava Indian mosaic bigeminivirus\infection\growth\cassava\varieties\yields\yield losses\crop losses\inoculum
AN: 0M07703140
TI: Cassava virus diseases and their control with special reference to southern Tanzania.
AU: Hillocks, R. J.
JN: Integrated Pest Management Reviews
YR: 1997
VL: 2
NO: 3
PP: 125-138
LA: En
MS: 63 ref.
AA: Natural Resources Institute, University of Greenwich, Chatham, Kent ME4 4TB, UK.
AB: Cassava is a major smallholder crop in much of Africa where it is attacked by 2 main virus diseases. African cassava mosaic disease (ACMD) [cassava African mosaic bigeminivirus (CAMV)] occurs almost everywhere that the crop is grown causing severe losses in some countries. Cassava brown streak disease (CBSD) [cassava brown streak potyvirus] is of more restricted distribution being prevalent mainly on the east African coast and shores of Lake Malawi. Although both diseases have been known for many decades and much is known about ACMD, the aetiology and epidemiology of CBSD remain poorly understood. Control measures for CAMV have been recommended and in some cases implemented in a number of countries. Resistant varieties have been developed and national research programmes and international agencies are supporting phytosanitation programmes, based mainly on the distribution of CAMV-free planting material. It is suggested that it may be possible to use the same control measures against CBSD but the lack of basic information on the disease and difficulties of disease diagnosis are obstacles to the design of control strategies. ACMD is found in most areas where CBSD occurs and control measures must consider the disease complex. The current knowledge about the 2 diseases is reviewed in the context of possible integrated control.
DE: cassava\Manihot esculenta\viruses\diseases\control\Tanzania\integrated control\plant disease control\plant diseases\plant pathogens\plant viruses\Africa\cassava African mosaic bigeminivirus\cassava brown streak potyvirus
GL: Tanzania\Africa
AN: 0M07703139
TI: The epidemic of cassava mosaic virus disease in Madagascar in the 1930s-1940s: lessons for the current situation in Uganda.
AU: Cours, G.\ Fargette, D.\ Otim-Nape, G. W.\ Thresh, J. M.
JN: Tropical Science
YR: 1997
VL: 37
NO: 4
PP: 238-248
LA: En
MS: 40 ref.
AA: Arboretum de la 'Bordette', 32480 La Romieu, France.
AB: The epidemic of cassava mosaic virus disease (CMD) [cassava African mosaic bigeminivirus] in Madagascar in the 1930s is compared with the epidemics that occurred in mainland Africa at the time and with the current one in Uganda. Before 1934, CMD was at an endemic stage in Madagascar in that there was a generally low incidence of the disease and losses were limited. A severe epidemic developed suddenly in 1934-36 and spread rapidly throughout the island. The susceptible local varieties were largely destroyed and there were serious shortages of cassava. A breeding programme was begun to develop CMD-resistant varieties by inter-crossing cultivated cassava (Manihot esculenta) with ceara rubber (M. glaziovii). The cultivars that were developed soon replaced the local varieties and disease incidence and losses returned to a low level. This precedent emphasizes the current role of such varieties, as CMD still causes serious crop losses in many parts of Africa and especially in Uganda, where the current epidemic is causing severe devastation.
DE: plant diseases\plant pathogens\plant viruses\plant disease control\disease resistance\epidemics\cassava African mosaic bigeminivirus\yield losses\crop losses\spread\varieties\Manihot esculenta\Manihot glaziovii\cultivars\reviews\cassava
GL: Madagascar\Uganda
AN: 0M07702180
TI: Host-associated strains within Ugandan populations of the whitefly Bemisia tabaci (Genn.), (Hom., Aleyrodidae).
AU: Legg, J. P.
JN: Journal of Applied Entomology
YR: 1996
VL: 120
NO: 9
PP: 523-527
LA: En
MS: 21 ref.
AA: International Institute of Tropical Agriculture, East and Southern African Regional Center, PO Box 7878, Kampala, Uganda.
AB: Studies were undertaken to investigate host relationships of populations of Bemisia tabaci taken from the major crop hosts in Uganda. B. tabaci adults taken from cotton and sweet potato did not colonize cassava. None survived for longer than 2 days and nymphs emerging from eggs laid on cassava died. Cassava B. tabaci in contrast showed limited colonization on cotton and sweet potato and adults emerging from cotton retained the ability to colonize cassava, confirming the genetic basis of the distinction between 'strains' suggested by previous isozyme studies. The implications of these findings with regard to the role of B. tabaci in the epidemiology of African cassava mosaic geminivirus [cassava African mosaic bigeminivirus] are discussed.
DE: Gossypium hirsutum\Manihot esculenta\Ipomoea batatas\insect pests\plant pests\plant viruses\cotton\sweet potatoes\cassava\Bemisia tabaci\Uganda\field crops\cassava African mosaic bigeminivirus\vectors\plant pathogens\transmission\transmission\insects\transmission\viruses\Big eminivirus
GL: Uganda
AN: 0E08503820\0M07606470
TI: Evidence that DNA-A of a geminivirus associated with severe cassava mosaic disease in Uganda has arisen by interspecific recombination.
AU: Zhou XuePing\ Liu YuLe\ Calvert, L.\ Munoz, C.\ Otim-Nape, G. W.\ Robinson, D. J.\ Harrison, B. D.
JN: Journal of General Virology
YR: 1997
VL: 78
NO: 8
PP: 2101-2111
LA: En
MS: 31 ref.
AA: Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK.
AB: Geminivirus isolates associated with an epidemic of severe cassava mosaic disease in Uganda were studied and compared with isolates from outside the epidemic area, cassava African mosaic bigeminivirus (ACMV) and East African cassava mosaic virus (EACMV). Isolates of a novel type (Uganda variant (UgV)) were detected in severely affected plants from the epidemic area, whereas those from plants outside the epidemic area were typical of ACMV. The complete nucleotide sequences of DNA-A of UgV (2799 nucleotides (nt)) and of a Tanzanian isolate of EACMV (2801 nt) were determined. Except for the coat protein (CP), they were extremely similar. The CP gene of UgV has 3 distinct regions: the 5' 219 nt are 99% identical to EACMV (only 79% to ACMV); the following 459 nt are 99% identical to ACMV (75% to EACMV); and the 3' 93 nt are 98% identical to EACMV (76% to ACMV). Therefore, it is suggested that UgV DNA-A has arisen via interspecific recombination of EACMV and ACMV. Despite the hybrid nature of their CP, UgV isolates were indistinguishable from ACMV in tests with 20 monoclonal antibodies, including 7 which reacted with ACMV but not EACMV. It is suggested that the discontinuous epitopes detected by these 7 MAbs involve amino acids which lie in the central part of the CP (residues 74-226) and which differ in ACMV and EACMV. UgV isolates were detected in severely affected plants from all 11 locations sampled. The probable role of recombination in geminivirus evolution in the short to medium term is discussed.
DE: cassava\Manihot esculenta\recombination\plant diseases\plant pathogens\plant viruses\cassava African mosaic bigeminivirus\East African cassava mosaic virus\viruses\molecular genetics\molecular genetics\monoclonal antibodies\coat proteins\evolution\recombination
AN: 0M07702179
TI: Detection of Indian cassava mosaic virus in meristem derived cassava plants by SR DAC-ELISA.
AU: Alagappan, M.\ Ramiah, M.\ Rajappan, K.
JN: Plant Disease Research
YR: 1997
VL: 12
NO: 1
PP: 56-58
LA: En
MS: 6 ref.
AA: Department of Plant Pathology, Tamil Nadu Agricultural University, Coimbatore 641003, India.
AB: Cassava Indian mosaic bigeminivirus (CIMV) was detected in infected leaves of 2 cassava cultivars and CIMV inoculated N. benthamiana plants using direct antigen coating-ELISA. Of 55 meristem-derived plants tested, 33 gave positive results.
DE: cassava Indian mosaic bigeminivirus\detection\cassava\Manihot esculenta\Nicotiana benthamiana\in vitro culture\tissue culture\plant diseases\plant pathogens\plant viruses\detection\immunodiagnosis
AN: 0M07701259
TI: The effects of cassava mosaic virus disease on yield and compensation in mixed stands of healthy and infected cassava.
AU: Otim-Nape, G. W.\ Thresh, J. M.\ Shaw, M. W.
JN: Annals of Applied Biology
YR: 1997
VL: 130
NO: 3
PP: 503-521
LA: En
MS: 20 ref.
AA: Namulonge Agricultural and Animal Production Research Institute, P O Box 7084, Kampala, Uganda.
AB: The effects of cassava mosaic virus disease (CMD)[cassava African mosaic bigeminivirus] on yield in fully and partly infected stands of cassava were investigated in field trials in Uganda during 1990-91 and 1991-92. Three cultivars (Ebwanateraka, Bao and Bukalasa 11), each at 3 levels of cutting infection (0%, 50% and 100%) and harvested 5, 10 and 15 months after planting (MAP) were used in a randomised block design with split-split plots and 4 replicates. Moreover, yield and growth data for individual infected and uninfected plants were considered in relation to the health status of their nearest neighbours. In each experiment, fresh tuberous root yields of plants from 100% infected plots gave significantly lower yields than those from 0% or 50% infected plots at each harvest date and the losses were greatest in cv. Bao. Yields of plants from 0% and 50% plots for each of the 3 cultivars were not significantly different, 10 and 15 MAP. The loss in yield differed between cultivars and harvest dates. Fresh stem, leaf and root yields and the number of tuberous roots were influenced by the health status of the plants harvested and that of their nearest neighbours. Uninfected plants surrounded by infected ones had more roots and heavier total fresh root, stem and leaf weights than those surrounded by uninfected ones. Overall, 26% and 42% compensation was recorded in 1990-91 and 1991-92, respectively. The effects of CMD on cassava production and of compensation in mixed stands of infected and uninfected plants are discussed, especially in relation to control strategies such as roguing.
DE: plant diseases\plant pathogens\plant viruses\cassava African mosaic bigeminivirus\cassava\yield losses\viruses\Bigeminivirus\crop losses
GL: Uganda
AN: 0M07701258
TI: Effect of cycocel on induction of biotic tolerance in cassava (Manihot esculenta).
AU: Onuegbu, B. A.
JN: Indian Journal of Agricultural Sciences
YR: 1997
VL: 67
NO: 6
PP: 275-276
LA: En
MS: 7 ref.
AA: Rivers State University of Science and Technology, Nkpolu, Port Harcourt, Nigeria.
AB: Most of the varieties of cassava grown in Nigeria are susceptible to various diseases including cassava mosaic disease [cassava african mosaic bigeminivirus], cassava bacterial blight caused by Xanthomonas campestris pv. manihotis [X. axonopodis pv. manihotis] and cassava anthracnose caused by Colletotrichum gloeosporioides f.sp. manihotis in association with the insect pest Pseudotheraptus devastans. An experiment was conducted in a plant-house to investigate the effects of Cycocel [chlormequat] on the performance of the highly susceptible cassava cv. Rose. There was an inverse relationship between Cycocel concentration and plant height, disease index and diameter of cortical and epidermal cells. With increasing concentration, Cycocel significantly increased stem biomass, root biomass and stem diameter. The role of Cycocel in improving tolerance in plants to pathogenic infection is discussed.
DE: plant diseases\plant pathogens\chemical control\plant disease control\Manihot esculenta\cassava\diseases\Nigeria\induced resistance\diseases\cassava African mosaic bigeminivirus\Xanthomonas axonopodis pv. manihotis\Colletotrichum gloeosporoides f.sp. manihotis\control\chlormequat\activity\diseases
GL: Nigeria
AN: 0M07609841
TI: Cassava mosaic virus disease in Uganda: the current pandemic and approaches to control.
AU: Otim-Nape, G. W.\ Bua, A.\ Thresh, J. M.\ Baguma, Y.\ Ogwal, S.\ Semakula, G. N.\ Acola, G.\ Byabakama, B.\ Martin, A.
YR: 1997
PP: 65 pp.
BN: ISBN 0-85954-466-4
LA: En
MS: 35 ref.
AA: Namulonge Agricultural and Animal Production Research Institute, P.O. Box 7084, Kampala, Uganda.
AB: The current pandemic of cassava mosaic virus disease [cassava African mosaic bigeminivirus] (CMD) in Uganda and various approaches to its control are described. Problems were first reported in 1988 in Luwero district where c. 2000 ha of cassava were severely affected. Similar reports were received from many other localities and the affected area has since extended progressively southwards moving along a broad front across much of Uganda and into western Kenya at c. 20 km/year. In the first attempts at control, CMD-free stem cuttings from relatively unaffected areas of southern Uganda were introduced into northern Luwero, Masindi, Arua, Nebbi, Moyo and Kumi districts and distributed to farmers for planting material. Spread of CMD to the introduced material occurred rapidly and within 8 months of planting there was almost total infection in all the fields surveyed and symptoms were severe. A different approach was adopted in Soroti district in 1991-93. Before introducing CMD-free planting material, extension staff were trained, and farmers were advised to destroy all CMD-infected material in the area before cuttings were planted. The results were generally satisfactory and little infection occurred so that clean planting material could be distributed to other farmers. Further attempts at control have been undertaken in many parts of Uganda since 1991, using CMD-resistant and other improved varieties selected through on-farm trials. Training is also being provided to extension staff and farmers and the improved varieties are being multiplied.
DE: plant diseases\plant pathogens\plant viruses\cassava\cassava African mosaic bigeminivirus\Uganda\control\viruses\Bigeminivirus\viruses\Bigeminivirus
GL: Uganda
AN: 0M07608101
TI: Disease development and recovery in resistant and susceptible cassava genotypes infected by African cassava mosaic geminivirus.
AU: Njock, T. E.\ Atiri, G. I.\ Thottappilly, G.\ Thresh, J. M.
JN: African Plant Protection
YR: 1996
VL: 2
NO: 2
PP: 97-102
LA: En
MS: 25 ref. AA: Department of Agricultural Biology, University of Ibadan, Ibadan, Nigeria.
AB: The incidence and severity of symptoms caused by cassava African mosaic bigeminivirus (CAMV) were assessed in shoots regenerated from single-node cuttings of 3 cassava genotypes differing in resistance to CAMV. Plants of the moderately resistant TMS 4(2)1425 and susceptible TMS 60506 did not recover from the disease as rapidly as those of the resistant TMS 30001. Recovery was manifested earlier on leaves of shoots from nodes collected from the shoot tip area than on those from below in all genotypes. Generally, a greater percentage of symptomless plants developed from single-node cuttings obtained from the apical region of infected plants than from the basal region, particularly in the resistant genotype. CAMV was detected serologically at greater concn in new axillary shoots regenerating from basal nodes of topped plants of the resistant genotype than from the apical nodes. Symptoms on shoots developing from apical cuttings were also less severe than on those from basal cuttings. Uninfected cuttings were obtained from some plants that had fully recovered from the disease, especially if the cuttings were obtained from young apical tissue.
DE: plant diseases\plant pathogens\plant viruses\disease resistance\recovery\cassava\cassava African mosaic bigeminivirus\epidemiology\varietal reactions\viruses\Bigeminivirus\viruses\Bigeminivirus\Manihot esculenta
AN: 0M07607296\0P06709519
TI: Transactivation of dianthin transgene expression by African cassava mosaic virus AC2.
AU: Hong YiGuo\ Saunders, K.\ Stanley, J.
JN: Virology (New York)
YR: 1997
VL: 228
NO: 2
PP: 383-387
LA: En MS: 22 ref.
AA: Department of Virus Research, John Innes Centre, Colney Lane, Norwich NR4 7UH, UK.
AB: A potato X potexvirus (PXV) was used to express the cassava African mosaic bigeminivirus transactivator protein, AC2, in planta in Nicotiana benthamiana. The activation of plant ribosome-inactivating protein (RIP) activity in transgenic plants was confirmed to be mediated by AC2; disruption of AC2 expression by introducing an in-frame stop codon or by deleting 5'-terminal or 3'-terminal coding sequences reduced RIP expression to the basal level associated with PXV-infected plants. AC2 expression from the PXV vector induced necrosis in nontransformed plants as well as in plants containing the RIP transgene. It is suggested that the protein could interact functionally with PXV and/or host factors. The potential of this system in providing a direct, sensitive assay for the investigation of the AC2 function in planta is discussed.
DE: plant diseases\plant pathogens\plant viruses\molecular genetics\potato X potexvirus\cassava African mosaic bigeminivirus\genetic engineering\viruses\Potexvirus\viruses\Bigeminivirus\Nicotiana benthamiana\genetic transformation\gene expression
AN: 0M07606242\0P06708704
TI: Resistance to Geminivirus infection by virus-induced expression of dianthin in transgenic plants.
AU: Hong YiGuo\ Saunders, K.\ Hartley, M. R.\ Stanley, J.
JN: Virology (New York)
YR: 1996
VL: 220
NO: 1
PP: 119-127
LA: En
MS: 57 ref.
AA: Department of Virus Research, John Innes Centre, Colney Lane, Norwich NR4 7UH, UK.
AB: Ribosome-inactivating proteins (RIPs) are naturally occurring plant toxins that exhibit antiviral activity against a diverse range of plant and animal viruses. The action of dianthin, a potent RIP isolated from carnation, was exploited to engineer resistance to a plant DNA virus, cassava African mosaic bigeminivirus (CAMV), in transgenic Nicotiana benthamiana. To achieve this, dianthin was expressed from the CAMV virion-sense promoter that is transactivated by the product of viral gene AC2. This avoids the need for constitutive expression of the RIP, facilitating regeneration of phenotypically normal plants, and ensures transgene expression is localized to virus-infected cells. When challenged with CAMV, transgenic plants produced atypical necrotic lesions on inoculated leaves, indicative of dianthin expression, viral DNA accumulation was significantly reduced in the tissues, and plants exhibited attenuated systemic symptoms from which they recovered. This phenotype holds for isolates of CAMV but not for other geminiviruses, suggesting that AC2 homologues from the latter are unable to efficiently transactivate the CAMV promoter.
DE: Dianthus caryophyllus\plant diseases\plant pathogens\plant viruses\phytotoxins\toxins\disease resistance\Nicotiana benthamiana\cassava African mosaic bigeminivirus\induced resistance\dianthin\genetic transformation\viruses\Bigeminivirus\molecular genetics\gene expression
AN: 0M07605845\7B00903055
TI: Unusually severe symptoms are a characteristic of the current epidemic of mosaic virus disease of cassava in Uganda.
AU: Gibson, R. W.\ Legg, J. P.\ Otim-Nape, G. W.
JN: Annals of Applied Biology
YR: 1996
VL: 128
NO: 3
PP: 479-490
LA: En
MS: 13 ref.
AA: Namulonge Agricultural and Animal Research Institute, PO Box 7084, Kampala, Uganda.
AB: Mosaic disease (MD) is more severe in cassava plants infected within the area of the current epidemic in northern and central Uganda than to the south of the affected area. This difference in severity was recorded within a single cultivar as well as amongst the mixtures of cultivars found commonly in fields. An increase in severity also occurred as the epidemic passed through localities. Varietal or agroecological factors coincident with the area of the epidemic are therefore unlikely to cause the increased severity. The severe disease could also be graft and cutting transmitted and could super-infect mildly diseased plants. Both mildly and severely diseased plants gave positive reactions in ELISA tests to antisera repared against cassava African mosaic bigeminivirus (ACMV) and an unusually severe form of ACMV or a closely related geminivirus is likely to be the cause of the severe mosaic disease. The epidemic also involves increased populations of the whitefly vector of ACMV, Bemisia tabaci, and possible hypotheses are presented as to how these phenomena may be related.
DE: plant diseases\plant pathogens\plant viruses\cassava\cassava African mosaic bigeminivirus\Uganda\epidemiology\viruses\Bigeminivirus
GL: Uganda
AN: 0M07605620
TI: Components of resistance of cassava to African cassava mosaic virus.
AU: Fargette, D.\ Colon, L. T.\ Bouveau, R.\ Fauquet, C.
JN: European Journal of Plant Pathology
YR: 1996
VL: 102
NO: 7
PP: 645-654
LA: En
MS: 37 ref.
AA: Laboratoire de Phytovirologie, ORSTOM, Adiopodoumé, Abidjan, Côte d'Ivoire.
AB: Components of resistance of cassava to cassava African mosaic bigeminivirus (ACMV) and their interrelationships were confirmed and quantified in a series of experiments at Adiopodoumé (Côte d'Ivoire, West Africa). The response to virus infection and to Bemisia tabaci infestation of a large collection of cassava, including local cultivars and others derived from inter-specific Manihot glaziovii hybrids was assessed. A consistent correlation was found between virus titre, symptom intensity, disease incidence and non-systemicity (recovery) which suggests that they are different expressions of the same genetic resistance. By contrast, there was no correlation between whitefly infestation and incidence of ACMV, suggesting that resistance to virus and vector are determined by 2 distinct genetic mechanisms. Several improved cultivars derived from inter-crossing cassava with M. glaziovii as well as some local cultivars were highly resistant and combined low susceptibility, low symptom intensity, low virus content and high level of recovery. Although yield losses ranged from 10% to 30% in such resistant cultivars, the combined effect of high field resistance and high rate of recovery lead to low disease incidence and limited yield losses, even in areas of high infection pressure such as Adiopodoumé.
DE: plant diseases\plant pathogens\plant viruses\disease resistance\insect pests\plant pests\disease vectors\varietal reactions\cassava\cassava African mosaic bigeminivirus\Cote d'Ivoire\genetics\transmission\breeding\yield losses\viruses\Bigeminivirus\crop losses\Bemisia tabaci\Manihot esculenta\vectors
GL: Cote d'Ivoire
AN: 0M07603834\0P06704934\0E08505578
TI: Virus resistance in Nicotiana benthamiana conferred by African cassava mosaic virus replication-associated protein (AC1) transgene.
AU: Hong YiGuo\ Stanley, J.
JN: Molecular Plant-Microbe Interactions
YR: 1996
VL: 9
NO: 4
PP: 219-225
LA: En
MS: 55 ref.
AA: Department of Virus Research, John Innes Centre, Colney Lane, Norwich NR4 7UH, UK.
AB: The replication-associated protein AC1 of cassava African mosaic bigeminivirus (CAMV) is essential for viral DNA replication. Transient expression of AC1 or the truncated N-terminal portion of the protein caused a significant reduction in the level of viral DNA replication in N. tabacum protoplasts. N. benthamiana plants were transformed with the AC1 coding sequence cloned downstream of the enhanced cauliflower mosaic caulimovirus 35S promoter. Five lines produced detectable levels of the appropriate-sized AC1-specific transcript, although none was able to complement the systemic infection of an CAMV AC1 mutant. However, all lines showed some level of resistance to CAMV infection; the majority of plants either remained asymptomatic or produced delayed and attenuated symptoms, and accumulated significantly reduced levels of viral DNA in comparison with infected control plants. In leaf disc assays, viral DNA replication was also reduced in transformed lines. None of the transformed lines showed resistance to the related viruses tomato golden mosaic bigeminivirus and beet curly top hybrigeminivirus, demonstrating the specific nature of the interaction. Possible mechanisms for the resistance phenomenon are discussed.
DE: plant diseases\plant pathogens\plant viruses\disease resistance\Nicotiana benthamiana\cassava African mosaic bigeminivirus\genetic transformation\resistance\molecular genetics\proteins\replication\viruses\Bigeminivirus
AN: 0M07600153\0P06700919
TI: Control of African cassava mosaic disease incidence and severity.
AU: Ogbe, F. O.\ Nnodu, E. C.\ Odurukwe, S. O.
JN: Tropical Science
YR: 1996
VL: 36
NO: 3
PP: 174-181
LA: En
MS: 15 ref.
AA: National Root Crops Research Institute, Umudike, PMB 7006, Umuahia, Nigeria.
AB: The age of mother plants used as a source of cuttings and the selection of plants free from symptoms of virus infection during the early stages of growth affected the incidence and severity of African cassava mosaic disease (caused by either cassava African mosaic bigeminivirus or East African cassava mosaic virus) in cuttings collected some months later. Cuttings from mother plants 6 and 8 months old sprouted and resulted in a significantly greater proportion of virus-infected plants than those from 10, 12 and 14-month-old plants. Incidence of mosaic disease was significantly reduced in plots established using cuttings from 12-month-old plants that were free of virus symptoms during inspection 1 or 2 months after planting. There was significant interaction between cultivar and selection of plants free from virus symptoms in reducing mosaic incidence. Mosaic severity was also significantly reduced. Cuttings from selected symptomless plants significantly increased tuberous root yield of cultivar TMS 30572 but not of cultivars NR 8082 and NR 8220. The use of resistant cultivars with crop sanitation would help to control the disease.
DE: plant diseases\plant pathogens\plant viruses\plant disease control\plant disease control\disease resistance\viruses\Bigeminivirus\cassava African mosaic bigeminivirus\cassava\cassava\East African cassava mosaic virus\control\viruses\unclassified viruses\East African cassava mosaic virus\viruses\cassava\cassava\control\viruses
AN: 0M07508099